Method for the preparation of an offset printing master



United States Patent 3,364,858 METHSD F61 THE PREPARATION OF AN SFFSETPRlNTlNG MAfiTER Yoshio Kojima, Toshimi Kishida, Masaaki Yoshiolra, andlsanru Fushiki, Tokyo, Japan, assignors to Konishiroku Photo Industry(10., Ltd, Tokyo, Japan, a corporation of Japan N0 Drawing. Filed Sept.9, 1964, Ser. No. 395,283 Claims priority, application Japan, Sept. 20,1963, 38/513,228 2 Claims. (Cl. 101-467) ABSTRACT 6F THE DISCLOSURE Ahydrophilic sheet such as paper bearing photographic or printed matter,is placed in contact with sheet of heatsensitive material and thensubjected to infrared radiation. This causes the heat-sensitive materialin contact with and corresponding to the photographic or printed matterto fuse and to form a tacky image to which a hydrophobic polymer powderis applied and then fixed as by treatment with solvent vapor or heat, toform an olfset printing master.

This invention relates to a method for the preparation of an offsetprinting master, and more particularly, to the preparation of an offsetmaster by fixation of a hydrophobic polymer material on theinfrared-absorbing image portion of a sheet bearing an image on ahydrophilic surface by the co-action of a heat-sensitive material alsopresent on the said image portion.

In accordance with a method of the present invention, there is prepareda sheet bearing a hydrophilic surface with an infrared-absorbing image,e.g., photographic, printed or hand-written figures or letters, on whichsheet a normally solid heat-sensitive material which can fuse, with orwithout decomposition, at a temperature as high as 50-150 C., leaving afluidized mass having dustadhering property is placed on the said imagearea.

This master unit is then subjected to infrared radiation thereby to formon the image portion such a fluidized mass as mentioned above. To thefluidized mass, a finely powdered composition mainly comprising ahydrophobic polymer material is applied, and then fixation is effectedin an appropriate manner depending on the property of the hydrophobicpolymer material, thereby to produce an offset printng master. Ifdesired, after-treatment is made so that the hydrophilic property of thesheet surface may be improved.

The preparation of an offset printing master of the enlarged size from aphotographic film by using an offset master paper is heretofore known inthe art. However, this is disadvantageous because of its requirement foran expensive apparatus and for complicated procedures.

The disadvantages of the prior art can be overcome by the presentinvention. That is to say, the present invention enables us to preparean offset printing master not only from a paper or the like containinghand-written or printed images, but also from a photographic printcontaining a photographic picture obtained by enlargement from amicrofilm or from a sheet containing a photographic picture obtained bya silver diffusion transfer process, without necessitating the use ofany expensive apparatus or complicated procedures. The offset printingmaster obtained by the present invention is of the lithographic typewith a slightly projected image portion, so that it is quiteink-receptive and allows of sharp printing.

It is accordingly one object of the present invention to provide asimple and economical method for the preparation of an offset printingmaster by utilization of a supercooling phenomenon.

Another object of the invention is to provide a method for thepreparation of an offset printing master from an original by directapplication of a heat-sensitive material thereto in which methodirnagewise fusion of a heat-sensitive material and the subsequentfixation are effected.

Still another object is to provide a method for the preparation of anoffset printing master from an original by indirect application of aheat-sensitive material theretoin which method imagewise fusion andtransfer of a heatsensitive material and the subsequent fixation areeffected.

Still another object of the invention is to provide a method for thepreparation of an offset printing master in which image formation with aheat-sensitive material and the subsequent fusion and fixation areeffected.

Other objects, features, capabilities and advantages of the presentinvention will be apparent from the description and claims which follow.

Now the present invention will be explained hereinbelow:

The heat-sensitive materials which can be placed on the image portion oforiginal are such materials which are normally solid and availablymaintained in the supercooled liquid or semi-solid state when they arefused with or without decomposition by heating and then cooled down to atemperature below their melting or decomposing point. Suitableheat-sensitive materials are those of highly dust-adhering property intheir supercooled state and sometimes they should preferably have atendency to be vaporized at a temperature above their melting ordecomposing point.

A likelihood of a heat-sensitive material to provide high dust-adhesionmay not only depend on the melting or decomposing point of the saidmaterial, but also it may be influenced by the inherent physicalproperties (e.g., dimensional structure of molecules, viscosity andsurface tension of the fused mass), purity, particle size of thematerial as well as the condition at which the material is heated orcooled. A period over which the material can provide high dust-adhesionalso varies depending on any of the afore-mentioned factors, and it willusually be within the range of from several minutes to several hours.Some of the heat-sensitive materials which will be specified later wouldbe able to exhibit dust-adhering property even over two days.

Various factors on which the durability (or stability) of thesupercooled state of a heat-sensitive material depends have beenstudied, and one of the important factors is found to be the particlesize of a heat-sensitive material. For example, benzotriazole orbenzotriazole-acetanilide combination can provide a greatly increasedlife time of their supercooled state in response to the decrease of theparticle size. (The term, a combination, used herein means that it isnot a simple mixture of the specified components and obtained by fusing,solidifying and then pulverizing the said simple mixture). At a certainlimit of particle size, the life time of the heat-sensitive material isincreased unexpectedly, and it is indicated that if the material has aparticle size below the critical limit, the supercooled state can bemaintained as long as several days. It is further assumed that asuitable combination of two substances, even if each of the saidsubstances has no good stability of the supercooled state, would behighly improved in its supercooling stability.

Generally speaking, a heat-sensitive material useful in the practice ofthe invention has a particle size ranging from 1 micron to microns,depending on the type and nature of the said material.

Suitable heat-sensitive materials may be either inorganic or organicsubstances, and various ones are useful for this invention. Typicalinorganic materials which melt with out decomposition or melt withvaporization include simple substances like sulfur and compounds likethe halides of a non-metal, e.g., antimony and phosphorus.Typical-organic materials include fructose, glucose, maltose or the likesugars; acids and their salts, such as benzoic acid, cinnamic acid,maleic anhydride, sebacic acid, malic acid, phthalic anhydride,potassium sodium tartrate, ammonium citrate, etc.; acid amides, such asacetanilide, phenacetin, acetylsemicarbazide and urea. Other organicsubstances have also been found to be suitable herein, which includesodium diethylthiocarbamate, iodoform, p-dimethylamino-benzaldehyde,methylhydroquinone, resorcine, l-phenyl-3-pyrazolidine, benzotriazole,dimedone, B-naphthol, sorbitol, etc. Use of a heat-sensitive materialwhich is normally solid and decomposes by heating also is possible. Thefluidized mass resulted from such heat-decomposable material willcomprise, in addition to the supercooled melt of the original material,the supercooled comelt of the decomposition products which may be thenormally solid material and the normally oily or semisolid material.Typical materials which will leave a liquid decomposate withdecomposition by heating are hydrazine sulfite,p-toluenesulfonylhydrazide, diphenyl-4,4-diazide, etc.

The heat-sensitive material mentioned above should be used in such astate that it is placed on the image area of an original from which anoffset printing master isto be produced. In one embodiment of thepresent invention, a heat-sensitive material is distributed directlyonto the image-bearing surface of an orginal by lightly rubbing saidsurface several times with an absorbent cotton, a felt, a cloth or thelike containing the fine powder of the heatsensitive material which hasbeen pulverized to the particle size of ll microns. An alternativemethod for forming a heat-sensitive layer directly on an originalcomprises dissolving a heat-sensitive material into a volatile solvent,spraying the resulted solution in an aerosol form onto the image-bearingsurface of an original or coating said solution onto the image-bearingsurface of an original with a brush, a cloth, a felt, an absorbentcotton or the like as impregnated with said solution and then drying theoriginal. In the latter case, it is important to be careful that ink ofthe letters or figures on the surface of an original if it ishand-written or printed should not be dissolved to blot on the surface.Further alternatively, the heat-sensitive material may be eitherincorporated into a paper stock or sized over the surface of papers, inorder to produce an offset printing master paper having an internal ortop layer of the heat-sensitive material. Still further, when aheat-sensitive material which is not decomposed by heat and which isconsiderably vaporizable, e.g., sulfur, is employed, it is possible tohave such heatsensitive material deposit thereon as a thin, uniformheatsensitive layer in vacuo.

In another embodiment of the present invention, the above heat-sensitivematerial may be used in a layer on a suitable support other than anoriginal. In other words, a specific heat-sensitive sheet comprising atransparent support and thereon a layer of the heat-sensitive materialis used in this embodiment. In order to prepare such a heat-sensitivesheet as referred to above, the following typical procedures will be inorder: The heatsensitive material, together with the small amount of abinder, is prepared as a solution or dispersion which is then applied orsprayed onto the surface of a transparent support which suitably is atracing paper, a cellophane or a plastic film. Alternatively, aheat-sensitive material being as fine as 1-100 microns in particle sizecan be rubbed onto the said surface to produce a useful heat-sensitivesheet. The heat-sensitive sheet thus prepared is brought into contactwith the image-bearing surface of an original, and then the composite isirradiated with infrared ray from the side of the said heat-sensitivesheet, so as to effect imagewise fusion and subsequent transfer of theheatsensitive material onto the image portion of the original which isthen further processed to have an offset printing master. 7 a

In still another embodiment of the present invention, imagewiseapplication of a heat-sensitive material is effected directly onto apaper which can be suitably processed to produce an offset printingmaster. The characteristic of this embodiment is that image formationwith and distribution of a heat-sensitive material on a sheet can becarried out at one time. In this preferable emf.

bodiment, for example, letters or figures or other images are printed ordrawn with an ink containing a heat-sensitive material on a suitablepaper. Handwriting, type-writing or printing can be employed at option.The printed or drawn paper is then processed by infrared irradiation andfixing to produce an offset printing master.

In the practice of the present invention, an original treated with theheat-sensitive material is subjected to infrared radiation, whereby theheat-sensitive material corresponding to the image portion is fused withor without decomposition and it remains as the fluidized mass havingdust-adhering property for a significant period even when it is cooledto room temperature. The image-bearing surface of the original is thentreated with the finely powdered hydrophobic polymer material so as tohave the polymer material adhere on the image portion only of theoriginal, and after an excess of the hydrophobic polymer material isremoved from the non-image portion, fixation is made over the wholesurface of the original. Alternatively, an untreated original is broughtinto contact with a heat-sensitive sheet on which a heat-sensitivematerial is present as a top layer and then the composite is subjectedto infrared radiation, whereby the heatsensitive material correspondingto the image portion is fused and transferred from the sheet to theimage portion of the original. After separation of the sheet from theoriginal, a fluidized mass having dust-adhering property on the imageportion of the original is treated with a hydrophobic polymer materialso as to effect selective adhesion of the material onto the imageportion of the" original. Fixation is conducted in the same manner asabove.

In carrying out infrared irradiation for the process of the presentinvention, it is convenient to use a quartz infrared lamp as a heatsource. Exposure should preferably be as short as possible in order tohave an effective utilization of heat uptaken by the image portion of anoriginal, while avoiding heat loss due to transport to the non-imageportion and this may be accomplished by employing a heat source having ahigh output. In general, when a quartz infrared lamp of 30-100 watts/cm.output is used, appropriate infrared radiation can be made at thedistance of 1 cm. from the radiation source for 0.05 to 1.0 sec. AThermofax copying machine (manufactured by Minnesota Mining & Mfg. Co.,USA.) may be conveniently used for this purpose.

A hydrophobic polymer material usable in this invention should be suchthat it can melt or soften at a comparatively low temperature or can beeasily dissolved in an organic solvent. Preferably, the hydrophobicpolymer material is used in the form of a fine powder having theparticle size of 5-100 microns. Suitable polymer materials arepolystyrene resin (for example, Piccolastic B75 and Piccolastic Dl00,both of which are commercially manufactured and sold by PennsylvaniaIndustrial and Chemical Co.), styrene-butadiene copolyrner resin (forexample, Pliolite S4, Pliolite S5 and Pliolite S6, all of which arecommercially manufactured and sold by Goodyear Tire & Rubber Co.),polyindenecournarone resin (for example, Cumar P-10 and Cumar P25, bothof which are commercially manufactured and sold by Allied ChemicalCorp.) and the like resins. Usually a toner usable for electrostaticphotographic processes can be employed for the instant purpose. By usinga colored pigment in combination with the polymer material, it ispossible to visually ascertain the degree of adhesion of the polymermaterial.

Fixation of the hydrophobic polymer material can be carried out byeither one of heating or solvent treatment, depending on the type of thesaid polymer material. If a heat-fusible resin is used as thehydrophobic polymer material, heating up to the softening point of theresin (usually 50200 C.) is sufiicient. Where a solventsoluble resin isused as the hydrophobic polymer material, the image-bearing surface tobe fixed is exposed to solvent vapor until the resin particles adheringon the image portion is converted to an aggregated mass. As apparent forthose skilled in the art, it is understood that the solvent used hereshould be a non-solvent for printing ink.

The original thus treated now has two portions, i.e., the image portionwhich is hydrophobic and the noniruage portion which is not hydrophobic,and so it is ready for use as an offset printing master. However, if thenonimage portion of the master is still insufiicient in hydrophilic oroleophobic property, it is advantageous to treat the said master with anetching solution which suitably is an aqueous solution of a hydrophilicpolymer substance, e.g., gum arabic, sodium carboxymethyl cellulose,etc., or an alkaline solution, for example, containing sodium hydroxideor sodium carbonate, or the mixture of these two solutions, therebyimproving the hydrophilic or oleophobic property of the non-image areaof the master. Usually for a commercially available photographic paper,such hydrophilic treatment is necessary or appropriate.

The following examples describe certain ways in which the principle ofthe invention has been applied, but are not to be construed as limitingits scope.

Example 1 Water (50 C.) 1 cc 750 Metol (Monomethyl p-aminophenolsulfate) g 2 Anhydrous sodium sulfite g 40 Hydroquinone .n g 8 Sodiumcarbonate (monohydrate) g 47 Potassium bromide g 2 Water to make 1 1After completion of the development, the print is processed in the usualmanner, i.e., by short stop, fixing, rinsing for 10 minutes and thendrying. The print thus obtained is used as an original.

Commercially available sulfur powder is rubbed over the image-bearingsurface of the original by means of a buffing roller. Then, the originalis subjected to infrared radiation using a 2,300 kw-output quartzinfrared lamp of 50 cm. long at the distance of 1 cm. from said originalat the relative speed of 12 cm./sec. Thereafter, Konifax toner PP (anelectrostatic photographic toner commercially manufactured and sold byKonishiroku Photo Industry Co., Ltd.) is dusted over the originaltrereby to have the toner adhere on the image portion. The toner on thenon-image portion is removed by the action of compressed air. Then,fixation of the image portion is made by irradiation from the saidquartz infrared lamp at the relative speed of 5 cm./sec., thereby toconverting the image portion to oleophilic.

The non-image portion of the original thus treated has insufiicienthydrophilic property and may be stained with ink. In order to avoidthis, surface treatment of the original is preferably made with anetching solution containing 0.5 g. sodium hydroxide and 0.05 g. sodiumcarboxymethyl cellulose in 100 cc. of Water. The original is now readyfor use as an offset printing master.

Example 2 In this example, an offset printing master is prepared byapplying a heat-sensitive material onto only the image portion of matterprinted on an art paper with an infrared-absorbing ink through imagewisetransfer of the heat-sensitive material from a heat-sensitive sheet, andthen fixing thereon a hydrophobic polymer material.

The heat-sensitive sheet used is prepared by strongly rubbing the finelypowdered benzotriazoleacetanilide (:25 by weight) combination with theparticle size of 1-100 microns over a tracing paper by means of abuffing roller, the said combination being obtained by mixing and fusingthe specified components and then pulverizing the fused mass.

The image-bearing surface of an original is brought into contact withthe heat-sensitive surface of the heatsensitive sheet, and then theresulted composite is subjected to infrared radiation from the side ofthe heatsensitive sheet in the same manner as in Example 1. Afterirradiation with infrared ray, the original is separated from theheat-sensitive sheet and then dusted with finely powdered PiccolasticD-75 so as to have it adhere on the image portion of said original.Fixation is elfected by using trichloroethylene vapor. Now the originalis ready for use as an offset printing master.

Example 3 On a photographic paper having a light-sensitive silverchlorobromide emulsion layer, a protective coating is provided by usingthe following formulation:

Gelatin g 1.6 p-Toluenesulfonylhydrazide (heat-sensitive material) tgWater cc The photographic paper with the protective coating is printedand processed by development, fixation and rinsing in the same manner asin Example 1, thereby to obtain an original. Then, the original issubjected to infrared irradiation with a quartz infrared lamp (same asthat of Example 1) at the distance of 1 cm. at the speed of 15 cm./sec.The original is treated with finely powdered Piccolastic D-75 in orderto make the image portion lipophilic and then immersed for 2 minutes foran etching solution of 0.2 g. of sodium hydroxide and 0.02 g. of sodiumcarboxymethyl-cellulose in 100 cc. of water in order to improve thelipophobic nature of the non-image portion. The original thus treated isready for use as an offset printing master.

Example 4 Typewriting is made on a commercially available offset masterpaper with a typewriting ribbon impregnated with an ink of the followingformulation:

G. Mineral oil 108 Carbon black 3O Oleic acid 20 Oil-soluble coloringmatter 5 Sebacic acid 3 Benzotriazole 1 75 portions.

What We claim is:

1. A method for the preparation of an offset printing master whichcomprises typewriting on paper having a hydrophilic surface with aninfrared absorbing ink containing powdered material which melts at 50 to150 C. and has a particle size Within the range of 1 to 100 microns,then irradiating the resulting type-written paper, with infraredirradiation and then dusting it with hydrophobic polymeric materialhaving a particle size of 1 to 100 microns whereby said polymericmaterial adheres to the type areas and fixing the adhered polymericmaterial to form the hydrophobic image portions of the printing master.

2. The method for the preparation of an ofiset printing master of claim1 wherein the powdered material contained in the ink is sebacic acid andbenzotriazole and the hydrophobic polymeric material iscournarone-indene resin.

References Cited UNITED STATES PATENTS 2,503,758 4/1950 Murray 101149.43,132,963 5/1964 Jarvis 101-149.4 3,196,029 7/1965 Lind 101-149.4 X3,260,612 7/1966 Dulmage et a1. 101-149.2 X

DAVID KLEIN, Primary Examiner.

